The present invention relates to an apparatus and method for sensing coins and other small discrete objects, and in particular to an apparatus which may be used in coin counting or handling.
A number of devices are intended to identify and/or discriminate coins or other small discrete objects. One example is coin counting or handling devices, (such as those described in U.S. patent application Ser. No. 08/255,539, now U.S. Pat. No. 5,564,546, and its continuation application Ser. No. 08/689,826, 08/237,486, now U.S. Pat. No. 5,620,079 and its continuation Ser. No. 08/834,952, filed Apr. 7, 1997, and 08/431,070, all of which are incorporated herein by reference). Other examples include vending machines, gaming devices such as slot machines, bus or subway coin or token xe2x80x9cfare boxes,xe2x80x9d and the like. Preferably, for such purposes, the sensors provide information which can be used to discriminate coins from non-coin objects and/or which can discriminate among different coin denominations and/or discriminate coins of one country from those of another.
Previous coin handling devices, and sensors therein, however, have suffered from a number of deficiencies. Many previous sensors have resulted in an undesirably large proportion of discrimination errors. At least in some cases this is believed to arise from an undesirably small signal to noise ratio in the sensor output. Accordingly, it would be useful to provide coin discrimination sensors having improved signal to noise ratio.
Many previous coin handling devices, and associated sensors, were configured to receive only one coin at a time, such as a typical vending machine which receives a single coin at a time through a coin slot. These devices typically present an easier coin handling and sensing environment because there is a lower expectation for coin throughput, an avoidance of the deposit of foreign material, an avoidance of small inter-coin spacing (or coin overlap), and because the slot naturally defines maximum coin diameter and thickness. Coin handlers and sensors that might be operable for a one-at-a-time coin environment may not be satisfactory for an environment in which a mass or plurality of coins can be received in a single location, all at once (such as a tray for receiving a mass of coins, poured into the tray from, e.g., a coin jar). Accordingly it would be useful to provide a coin handler and/or sensor which, although it might be successfully employed in a one-coin-at-a-time environment, can also function satisfactorily in a device which receives a mass of coins.
Many previous sensors and associated circuitry used for coin discrimination were configured to sense characteristics or parameters of coins (or other objects) so as to provide data relating to an average value for a coin as a whole. Such sensors and circuitry were not able to provide information specific to certain regions or levels of the coin (such as core material vs. cladding material). In some currencies, two or more denominations may have average characteristics which are so similar that it is difficult to distinguish the coins. For example, it is difficult to distinguish U.S. dimes from pre-1982 U.S. pennies, based only on average differences, the main physical difference being the difference in cladding (or absence thereof). In some previous devices, inductive coin testing is used to detect the effect of a coin on an alternating electromagnetic field produced by a coil, and specifically the coin""s effect upon the coil""s impedance, e.g. related to one or more of the coin""s diameter, thickness, conductivity and permeability. In general, when an alternating electromagnetic field is provided to such a coil, the field will penetrate a coin to an extent that decreases with increasing frequency. Properties near the surface of a coin have a greater effect on a higher frequency field, and interior material have a lesser effect. Because certain coins, such as the United States ten and twenty-five coins, are laminated, this frequency dependancy can be of use in coin discrimination, but, it is believed, has not previously been used in this manner. Accordingly, it would further be useful to provide a device which can provide information relating to different regions of coins or other objects.
Although there are a number of parameters which, at least theoretically, can be useful in discriminating coins and small objects (such as size, including diameter and thickness), mass density, conductivity, magnetic permeability, homogeneity or lack thereof (such as cladded or plated coins), and the like, many previous sensors were configured to detect only a single one of such parameters. In embodiments in which only a single parameter is used, discrimination among coins and other small objects was often inaccurate, yielding both misidentification of a coin denomination (false positives), and failure to recognize a coin denomination (false negatives). In some cases, two coins which are different may be identified as the same coin because a parameter which could serve to discriminate between the coins (such as presence or absence of plating, magnetic non-magnetic character of the coin, etc.) is not detected by the sensor. Thus, using such sensors, when it is desired to use several parameters to discriminate coins and other objects, it has been necessary to provide a plurality of sensors (if such sensors are available), typically one sensor for each parameter to be detected. Multiplying the number of sensors in device increases the cost of fabricating, designing, maintaining and repairing such apparatus. Furthermore, previous devices typically required that multiple sensors be spaced apart, usually along a linear track which the coins follow, and often the spacing must be relatively far apart in order to properly correlate sequential data from two sensors with a particular coin (and avoid attributing data from the two sensors to a single coin when the data was related, in fact, to two different coins). This spacing increases the physical size requirements for such a device, and may lead to an apparatus which is relatively slow since the path which the coins are required to traverse is longer.
Furthermore, when two or more sensors each output a single parameter, it is typically difficult or impossible to base discrimination on the relationship or profile of one parameter to a second parameter for a given coin, because of the difficulty in knowing which point in a first parameter profile corresponds to which point in a second parameter profile. If there are multiple sensors spaced along the coin path, the software for coin discrimination becomes more complicated, since it is necessary to keep track of when a coin passes by the various sensors. Timing is affected, e.g., by speed variations in the coins as they move the coin path, such as rolling down a rail.
Even in cases where a single core is used for two different frequencies or parameters, many previous devices take measurements at two different times, typically as the coin moves through different locations, in order to measure several different parameters. For example, in some devices, a core is arranged with two spaced-apart poles with a first measurement taken at a first time and location when a coin is adjacent a first pole, and a second measurement taken at a second, later time, when the coin has moved substantially toward the second pole. It is believed that, in general, providing two or more different measurement locations or times, in order to measure two or more parameters, or in order to use two or more frequencies, leads to undesirable loss of coin throughput, occupies undesirably extended space and requires relatively complicated circuits and/or algorithms (e.g. to match up sensor outputs as a particular coin moves to different measurement locations).
Some sensors relate to the electrical or magnetic properties of the coin or other object, and may involve creation of an electromagnetic field for application to the coin. With many previous sensors, the interaction of generated magnetic flux with the coin was too low to permit the desired efficiency and accuracy of coin discrimination, and resulted in an insufficient signal-to-noise ratio.
Many previous coin handling devices and sensors had characteristics which were undesirable, especially when the devices were for use by untrained users. Such previous devices had insufficient accuracy, short service life, had an undesirably high potential for causing user injuries, were difficult to use, requiring training or extensive instruction, failed, too often, to return unprocessed coins to the user, took too long to process coins, had an undesirably low throughput, were susceptible to frequent jamming, which could not be cleared without human intervention, often requiring intervention by trained personnel, could handle only a narrow range of coin types, a denominations, were overly sensitive to wet sticky coins or foreign or non-coin objects, either malfunctioning or placing the foreign objects in the coin bins, rejected an undesirably high portion of good coins, required frequent and/or complicated set-up, calibration or maintenance, required too large a volume or footprint were overly-sensitive to temperature variations, were undesirably loud, were hard to upgrade or retrofit to benefit from new technologies or ideas, and/or were difficult or expensive to design and manufacture.
Accordingly, it would be advantageous to provide a coin handler and/or sensor device having improved discrimination and accuracy, reduced costs or space requirements, which is faster than previous devices, easier or less expensive to design, construct, use and maintain, and/or results in improved signal-to-noise ratio.
The present invention provides a device for processing and/or discriminating coins or other objects, such as discriminating among a plurality of coins or other objects received all at once, in a mass or pile, from the user, with the coins or objects being of many different sizes, types or denominations. The device has a high degree of automation and high tolerance for foreign objects and less-than-pristine objects (such as wet, sticky, coated, bent or misshapen coins), so that the device can be readily used by members of the general public, requiring little, if any, training or instruction and little or no human manipulation or intervention, other than inputting the mass of coins.
According to one embodiment of the invention, after input and, preferably, cleaning, coins are signulated and move past a sensor for discrimination, counting and/or sorting. In general, coin slowing or adhesion is reduced by avoiding avoiding extensive flat regions in surfaces which contact coins (such as making such surfaces curved, quilted or dimpled). Coin paths are configured to flare or widen in the direction of coin travel to avoid jamming.
A signulating coin pickup assembly is preferably provided with two or more concentrically-mounted disks, one of which includes an integrated exit ledge. Movable paddles flex to avoid creating or exacerbating jams and deflect over the coin exit ledge. Vertically stacked coins tip backwards into a recess and slide over supporting coins to facilitate singulation. At the end of a transaction, coins are forced along the coin path by a rake, and debris is removed through a trap door. Coins exiting the coin pickup assembly are tipped away from the face-support rail to minimize friction.
According to one embodiment of the present invention, a sensor is provided in which nearly all the magnetic field produced by the coil interacts with the coin providing a relatively intense electromagnetic field in the region traversed by a coin or other object. Preferably, the sensor can be used to obtain information on two different parameters of a coin or other object. In one embodiment, a single sensor provides information indicative of both size, (diameter) and conductivity. In one embodiment, the sensor includes a core, such as ferrite or other magnetically permeable material, in a curved (e.g., torroid or half-torroid) shape which defines a gap. The coin being sensed moves through the vicinity of the gap, in one embodiment, through the gap. In one embodiment, the core is shaped to reduce sensitivity of the sensor to slight deviations in the location of the coin within the gap (bounce or wobble). As a coin or the object passes through the field in the vicinity of the gap, data relating to coin parameters are sensed, such as changes in inductance (from which the diameter of the object or coin, or portions thereof, can be derived), and the quality factor (Q factor), related to the amount of energy dissipated (from which conductivity of the object or coin, or portions thereof, can be obtained).
In one embodiment, data relating to conductance of the coin (or portions thereof) as a function of diameter are analyzed (e.g. by comparing with conductance-diameter data for known coins) in order to discriminate the sensed coins. Preferably, the detection procedure uses several thresholds or window parameters to provide high recognition accuracy.
According to one aspect of the invention, a coin discrimination apparatus and method is provided in which an oscillating electromagnetic field is generated on a single sensing core. The oscillating electromagnetic field is composed of one or more frequency components. The electromagnetic field interacts with a coin, and these interactions are monitored and used to classify the coin according to its physical properties. All frequency components of the magnetic field are phase-locked to a common reference frequency. The phase relationship between the various frequencies are locked in order to avoid interference between frequencies and with any neighboring cores or sensors and to facilitate accurate determination of the interaction of each frequency component with the coin.
In one embodiment, low and high frequency coils on the core form a part of oscillator circuits. The circuits are configured to maintain oscillation of the signal through the coils at a substantially constant frequency, even as the effective inductance of the coil changes (e.g. in response to passage of a coin). The amount of change in other components of the circuit needed to offset the change in inductance (and thus maintain the frequency at a substantially constant value) is a measure of the magnitude of the change in the inductance caused by the passage of the coin, and indicative of coin diameter.
In addition to providing information related to coin diameter, the sensor can also be used to provide information related to coin conductance, preferably substantially simultaneously with providing the diameter information. As a coin moves past the coil, there will be an amount of energy loss and the amplitude of the signal in the coil will change in a manner related to the conductance of the coin (or portions thereof). For a given effective diameter of the coin, the energy loss in the eddy currents will be inversely related to the conductivity of the coin material penetrated by the magnetic field.
Preferably, the coin pickup assembly and sensor regions are configured for easy access for cleaning and maintenance, such as by providing a sensor block which slides away from the coin path and can be re-positioned without recalibration. In one embodiment, the diverter assembly is hinged to permit to be tipped outward for access. Preferably, coins which stray from the coin path are deflected, e.g. via a ramped sensor housing and/or bypass chutes, to a customer return area.
Coins which are recognized and properly positioned or spaced are deflected out of the default (gravity-fed) coin path into an acceptance bin or trolley. Any coins or other objects which are not thus actively accepted travel along a default path to the customer return area. Preferably, information is sensed which permits an estimate of coin velocity and/or acceleration so that the deflector mechanism can be timed to deflect coins even though different coins may be traveling at different velocities (e.g. owing to stickness or adhesion). In one embodiment, each object is individually analyzed to determine if it is a coin that should be accepted (i.e. is recognized as an acceptable coin denomination), and, if so, if it is possible to properly deflect the coin (e.g. it is sufficiently spaced from adjacent coins). By requiring that active steps be taken to accept a coin (i.e. by making the default path the xe2x80x9crejectxe2x80x9d path), it is more likely that all accepted objects will in fact be members of an acceptable class, and will be accurately counted.